1. Field of the Invention
This invention relates to fixed wireless access communication networks, and in particular to a method of passing directory numbers of a called party between a central office and a PBX over a wireless link.
2. Background Art
Wireless access technology was initially developed to provide phone services to remote communities. As technology improved and cost came down, this basic service has advanced from voice only transmissions in the rural areas, to voice, data, fax and other telecommunication service in the rural, sub-urban and urban areas. With the demand for wireless communication on a continuous rise, subscribers expect to receive the same full range of services that are beginning to emerge in the wireline environment, such as data, video telephony, video-on-demand, and also they increasingly expect voice and data quality that is equal to, or better than in wireline telephone systems.
The main difference between wireless access, cellular, and PCS systems is that the wireless access technology is not designed for mobility, and as such, systems do not allow for roaming and provide only limited cell site hand-off. Nevertheless, the existing cellular systems standards were adopted for the wireless access, since the protocols for establishing the connection and communication between a customer and the service provider are similar.
An emerging system architecture named fixed wireless (radio) access, also known as wireless local loop, or fixed radio, provides telephone, facsimile and data services to individual business and residential subscribers. A fixed wireless system comprises two main elements: a base station (or base), located at a cell site, and telephone stations located at the customer's premise, each equipped with a radio unit. If more than one telephone station is provided, all have the same destination address. The subscriber premise may also be equipped with a residential junction unit (RJU), which provides one or more independent telephone jacks for each subscriber. The base station is connected to standard switches in the public network through copper cables, optical fiber, or microwave links. A base station includes microwave radio units, which supply a two-way radio link between the stations at the subscriber premise and the base station.
A more recent architecture for fixed wireless radio access systems was designed for providing wireless communications between a cell site and a private branch exchange (PBX) installed at the customer premise, a plurality of on-premise subscriber stations being connected to the PBX over cabled connections. A PBX, which is a switching center, typically has a trunk connection to a central office, which is also a switching center. To transmit information between the PBX and the switching center over a wireless link, it is necessary for the wireless link to appear to the PBX as a central office trunk with direct inward/outward dial capabilities.
Such an architecture is disclosed in U.S. Pat. No. 5,787,355 (Bannister et al., filed on Apr. 22, 1994 and assigned to Northern Telecom Limited). For direct inward dial (DID) calls, the wireless system passes on an air interface to a radio unit (RU), and from there to the PBX, information on the called party, so that an incoming call can be presented to the proper phone in the PBX, by making the interface between the RU and the PBX look like a central office trunk, as per LSSGR FR-NWT-000064 BellCORE specification.
The system disclosed in Bannister's application can be configured with a plurality of RUs, each RU responding to a plurality of mobile identification numbers (MINs). A master radio unit controls a bank of slave RUs to route a call. To this end, a RU has a transceiver section which establishes a communication link between the PBX and the base station under the supervision of a programmable control unit, and a re-programmable memory for storing information such as MIN lists or MIN to station directory numbers (DN), or PBX address correlation information.
According to the present invention, for an incoming call originating in the public switched telephone network (PSTN) and directed to a user station in the PBX, the DN of the called party is passed on from the central office switch to a cell station, from the cell station to a wireless trunk interface (WTI) over a wireless link, and from there to the PBX, so that the connection is established with the proper station behind the PBX.
For calls originating from a user station behind the PBX to a called party in the PSTN, the DN of the calling party is passed on from the PBX to the WTI, and from there, over a wireless link to the cell station and to the central office switch, so that the calling party DN is presented to the switch. The DN of the calling party may be used, for example, for billing purposes.
In other words, the invention is directed to a wireless radio access system provided with a direct inward dial (DID) and an automatic identification outward dialling (AIOD) function, for passing the directory number (DN) between the service provider and the customer. The DID and AIOD functions are implemented using the fast/slow associated control channel of the air interface.